Impact hydraulic forming device

ABSTRACT

An impact hydraulic forming device has a hydraulic pressure chamber with a bore filled with water, and a plunger is arranged to be thrust into the bore by a hammer which is unitary with the plunger and which is reciprocable in a cylinder. Means are provided to direct a jet of water across the open end of the bore in such a way as to seal the water in the bore from flowing out of the bore, to provide a water membrance. The face of the hammer joined to the plunger has an annular recess of curvilinear cross section whose surface merges smoothly with the exterior surface of the plunger, and air jet means are arranged to be directed against this annular groove to retract the hammer. The hammer is advanced under air pressure for a pair of its stroke after which the pressure air is shut off and the advance of the hammer is carried out by expansion of the air in the cylinder. The air jets directed against the recessed end face of the hammer are also shut off after the hammer has completed part of its return stroke, with the return stroke being completed due to the expansion of the air jetted into the cylinder. Valve means control reciprocation of the hammer, and the valve means may be flow pressure operated valves of may be solenoid valve controlled by an electrical control device.

United States Patent 191 Tominaga et al.

[ IMPACT HYDRAULIC FORMING DEVICE [75] Inventors: Hiroshi Tominaga,Masanobu Takamatsu, both of Yokohama,.lapan [73] Assignee: Tokyu SharyoSeizo Kabushiki Kaisha, Tokyo, Japan [22] Filed: April 23, 1971 [21]Appl. No.: 136,685

[52] US. Cl. ..60/54.5 H, 60/546 HA, 417/403, 417/489, 137/815 3,601,9888/1971 Chermensky et al. ....60/54 6 HA 3,207,442 9/1965 Kessler et a1...4l7/403 3,500,641 3/1970 Meekings 60/546 HA 3,412,554 11/1968Voitsckhovsky ..60/l0.5 2,726,642 10/1955 Zinty et a1. ..91/2902,955,749 10/1960 Tomkowiak ..92/l81 R FOREIGN PATENTS OR APPLICATIONSGreat Britain ..60/54.5 HA

l lMarch 20, 1973 Primary Examiner-Martin P. Schwadron AssistantExaminer-A. M. Zupcic Att0rney-John J. McGlew and Alfred E. Page [5 7ABSTRACT An impact hydraulic forming device has a hydraulic pressurechamber with a bore filled with water, and a plunger is arranged to bethrust into the bore by a hammer which is unitary with the plunger andwhich is reciprocable in a cylinder. Means are provided to direct a jetof water across the open end of the bore in such a way as to seal thewater in the bore from flowing out of the bore, to provide a watermembrance. The face of the hammer joined to the plunger has an annularrecess of curvilinear cross section whose surface merges smoothly withthe exterior surface of the plunger, and air jet means are arranged tobe directed against this annular groove to retract the hammer. Thehammer is advanced under air pressure for a pair of its stroke afterwhich the pressure air is shut off and the advance of the hammer iscarried out by expansion of the air in the cylinder. The air jetsdirected against the recessed end face of the hammer are also shut offafter the hammer has completed part of its return stroke, with thereturn stroke being completed due to the expansion of the air jettedinto the cylinder. Valve means control reciprocation of the hammer, andthe valve means may be flow pressure operated valves of may be solenoidvalve controlled by an electrical control device.

7 Claims, 4 Drawing Figures IMPACT HYDRAULIC FORMING DEVICE SUMMARY OFTHE INVENTION highly pressurize the water in the hydraulic pressurechamber instantenously, thus performing metal forming or other working.

In conventional impact hydraulic forming devices of the type describedabove, if the device is to be horizontally installed, the plunger isinserted into the hydraulic pressure chamber in advance to prevent waterfrom flowing out of the chamber and a separate hammer imparts blows ontothis plunger indirectly. Therefore, in comparison with the devices ofthe type wherein a plunger is directly thrust, the conventional devicesincur loss in energy transmission and the efficiency of producing impacthydraulic pressure is lower. In reciprocating the hammer, the advancingmotion of the hammer is accomplished only by means of the pressure ofcompressed air, and therefore the consumption rate of compressed air isincreased and the energy is not utilized effectively. The return motionof the hammer is accomplished by the suction of the hammer at its rearend portion or by means of the pushing force produced by compressed air,supplied from the hydraulic pressure chamber located in front of thehammer. In the former case, a large-scale device is required.Furthermore, the valve mechanism thereof is subject to severe workingconditions where both high hydraulic pressure and air pressure areencountered, and therefore the valve mechanism is liable to malfunction.In the latter case, there is a drawback that the consumption rate ofcompressed air is increased. Additionally, an effective devices havemany drawbacks.

An object of this invention is to thrust a plunger directly by forming awater membrane, at the opening .of a hydraulic pressure chamber,through-which the I plunger is thrust and filling the chamber withwater, re-

gardless of the installing location of the device.

Another object of this invention is to utilize the energy of compressedair economically by accomplishing the advancing motion of a hammer notonly by the pressure of compressed air but also by the energy producedfrom the expansion of compressed air.

Still another object of this invention is to accomplish the motion ofthe hammer in a short period of time by a small amount of low pressurecompressed air through the utilization of the dynamic pressure of thejet effect obtained by injecting compressed air.

A further object of this invention is to accomplish the reciprocatingmotion of the hammer by utilizing the pressure of working compressedair, or by electrical control, thus making it possible to produce impacthydraulic pressure continuously.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIG. 1is a sectional view, partly schematic, of the impact hydraulic formingdevice according to this invention in which the reciprocating motion ofa hammer is accomplished by air pressure;

FIG. 2 is an enlarged, detailed, sectional view of the principal portionof a means for sealing the hydraulic pressure producing water which isemployed in the device shown in FIG. 1;

FIG. 3 is a sectional view, partly schematic, of another impacthydraulic forming device in which a means for opening and closing theinside of a cylinder is added to the embodiment shown in FIG. 1; and

FIG. 4 is a sectional view, partly schematic, of still another impacthydraulic forming device embodying this invention in which thereciprocating motion of the hammer is electrically accomplished.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, acylinder 1 has a hammer 3, integral with a plunger 2, movable therein.Formed at the front end of the cylinder 1 is a water membrane chamber 6of a hydraulic pressure producing water sealing means which is separatedfrom the cylinder 1 by a stepped portion 5 having an opening 4. Thewater membrane chamber 6 communicates with a plunger bore 8 of ahydraulic pressure chamber 7. A water channel 1 1, having a feed valve 9and leading to a water source 10, and a water channel 12, leading to aforming die (not shown), are in communication with bore 8.

As illustrated in detail in FIG. 2, the water membrane chamber 6comprises a wall surface 13 which is at right angles to the center lineof the plunger bore 8, a water outlet 14, having a valve 59, which isinclined from wall surface 13 by a small angle 11: to guide a high speedwater jet, an outlet 15 for discharging water from the water membranechamber 6, and an air vent 16 in communication with atmosphere. Byvirtue of this construction, a high speed water jet is injected from-thewater outlet 14 against the opening between the wall surface 13 and theplunger bore 8, thus forming a water membrane of comparatively smallthickness to cover the entire area of the opening. When the watermembrane is to be formed, a hydraulic pressure having a somewhatdifferent direction is applied in opposition to the water which tends toflow out of the opening of the wall surface 13, thereby to prevent thewater in the plunger bore 8 from flowing out. In this way, the watersupplied into the plunger bore 8 from the water source 10 through thefeed valve 9 is sealed within the bore 8, thus making it possible tothrust the plunger 2 directly. Since the head of the water in theplunger bore 8 is practically 1 meter or so at most, the inclinationangle :1; can be selected within the range of 2 to 5 by increasing theflow rate for forming the water membrane appropriately. As soon as thefeed of water to the plunger bore 8 is started, the formation of thewater membrane is started. When the water is fully charged, the plunger2 is immediately thrust. Therefore, the time required for the formationof water membrane is l to 2 seconds at most in practice. Consequently,the amount of water required is small. The important point to note hereis that when the plunger 2 is to be thrust into the plunger bore 8, thetip of the plunger 2 crashes into the water membrane and is thrust afterbreaking through the water membrane. Therefore, if the water membrane isinclined in either direction, the plunger 2 is given a thrust in thehorizontal direction under the influence of the inclined water membraneand is pressed against one direction of the inner surface of the plungerhole 8. This is not desirable, because frictional resistance loss iscaused. in accordance with this invention, however, it is possible tomaintain the water membrane so as to form a centered curved surface withrespect to the vertical and horizontal directions by appropriatelyselecting the position and the angle of the water inlet 14 with respectto the wall surface 13 and controlling the flow rate within anappropriate range. Thus, the abovedescribed drawback can be eliminated.

The hammer 3 integral with the plunger 2 has recessed portions 17 whichare formed at the junction of the hammer and plunger, so that they mergesmoothly with the outer circumference of the plunger 2. The steppedportion 5 is provided with a plurality of returning air ports 18opposite the recessed portions 17 of the hammer 3. In returning thehammer after the plunger 2 is thrust into the plunger bore 8 and impacthydraulic pressure is produced, compressed air is injected fromreturning air ports 18 to the recessed portions 17 of the hammer 3. Atthis time, the injected compressed air impinges against the recessedportions 17, changes its course by nearly 180 and is reflected. Due tothe changes in the momentum of this jet effect, a thrust twice as largeas that obtained by injecting compressed air against a flat surface isprovided, and the hammer 3 is returned to its initial position in aquite short time interval of about 0.5 second. Thus, the hammer 3 isreturned by a small amount of low pressure compressed air. In injectingcompressed air from the returning air ports 18, a strong thrust isapplied from a plurality of air ports 18 for the period of time of 0.1to 0.2 second during the early part of the hammer return. After thehammer 3 is given a sufficient speed, the air jet thrust is terminated.In this way, the dynamic pressure of the air is more effectivelyutilized and strong shock by the hammer due to its return can beavoided. The important points to note here are that a large impact forceis applied to the plunger 2 when the plunger 2 compresses the water inthe hydraulic pressure chamber 7 momentarily, and that there is apossibility of incurring damage due to the stress concentration at thejunction between the plunger 2 and the hammer 3. According to thisinvention, however, the recessed portions 1] merge smoothly with theplunger 2 and their cross-sectional areas are successively increased,and therefore excessive stress concentration is not caused.Consequently, the durability of the plunger 2 is quite high.

The cylinder 11 has a compressed air feed port 19 at the rear endthereof. A main feed valve 25, having a valve body 24 provided with aspring 23 at the back side thereof, is installed on an air pipe 22between the supply port 19 and an air source 21. The air pipe 22 isprovided with an operating valve 20. An auxiliary feed valve 26, havinga spring 37 at the back side thereof, is provided adjacent to the mainfeed valve 25. The auxiliary feed valve 26 is also provided with a smallpiston 28, a valve body 29 and a large piston 30 which are all madeintegral and concentric with a trigger rod 27 protruding inside of thecylinder 1. The auxiliary feed valve 26 communicates with the rear endof the cylinder 1 through an air pipe 31, and communicates with valve 25through an air pipe 32 branched from the air pipe 22. Valve 26 is alsoin communication with the rear end of the valve body 24 of the main feedvalve 25 through a passage 33. Furthermore, the auxiliary feed valve 26is provided with a discharge port 34. Moreover, the rear end of thelarger piston 30 communicates through an air pipe 35 with a cut-off airport 36 which is determined so as to provide a desired air expansioncoefficient with respect to the total working stroke of the hammer 3.Before the hammer 3 makes an advancing stroke, the hammer is positionedat the rear end of the cylinder 1, as a result of which the trigger rod27 is pushed to the right. Therefore, in the auxiliary feed valve 26,the small piston 28 closes the air pipe 32 and the valve body 29 opensthe exhaust port 34, thus opening the passage 33 to atmosphere. The mainfeed valve 25 is opened by moving the valve body 24 against the bias ofthe spring 23 by means of the compressed air supplied from the airsource 21. Thus, compressed air is directed into the cylinder 1 to movethe hammer 3. When the advancing motion of the hammer 3 is started, theair pressure in the cylinder 1 is directed through the air pipe 31 intothe auxiliary feed valve 26 and is applied onto the small piston 28 tohold the trigger rod 27 in its retracted position. Consequently, themain feed valve 25 is opened and the feed of compressed air iscontinued. Thus, the hammer 3 advances within the cylinder 1 and passesby the cut-off air port 36. At this time, the air pressure in thecylinder 1 is applied from the cut-off air port 36 through the air pipe35 onto the large piston 30 of the auxiliary feed valve 26. As a result,the trigger rod 27 is projected and the small piston 28 opens the airpipe 32. Compressed air is applied through the passage 33 onto the backof the valve body 24 of the main feed valve 25, and the valve body 29closes the discharge port 34. Consequently, the main feed valve 25 isclosed and the delivery of compressed air is stopped. From this time on,the hammer 3 is accelerated due to the expansion of compressed air inthe cylinder 1 and helps the plunger 2 in producing the impact hydraulicpressure.

The cylinder 1 is provided with an exhaust port 37 at the rear endthereof. An air pipe 39 is provided to connect exhaust port 37' and adischarge port 38. A return valve 41 is provided in an air pipe 40 whichis branched from the air pipe 22 and is connected to returning air ports18. The return valve 41 comprises a first land 44, which is integral andconcentric with a valve spool 43, having a spring 42 at the back endthereof and which opens or closes the air pipe 39, and a second land 45which opens or closes the air pipe 40. A motion stop valve 46 isprovided on the air pipe 40. Moreover, the cylinder 1 is provided withan air inlet 47 at a position ahead of the cut-off air port 36 butwithin the total working stroke of the hammer 3. A cushion valve 49 isprovided in an air pipe 48 connected to air inlet 47. The cushion valve49 has a piston 50 which is provided integral with the spool 43 of thereturn valve 41 on the opposite end from the spring 42. The air pipe 48communicates with the piston 50 through a throttle 51 and a ball valve53 biased by a spring 52. During the abovedescribed advancing motion ofthe hammer 3, the pressure at the air inlet 47 becomes equal toatmospheric pressure and the return valve 41 is held in the illustratedposition by the bias of spring 42, and is therefore preventing returnmotion of the hammer. After the advancing stroke of the hammer 3 iscompleted, the hammer 3 passes by the position of the air inlet 47. Atthis time, the air pressure in the cylinder 1 is applied from the airinlet 47 through the air pipe 48 onto the piston 50 of the cushion valve49. Consequently, the return valve 41 is moved to the right and thecylinder 1 is exhausted by means of the first land 44 opening pipe 39.At the same time, compressed air is injected from the returning airports 18 through the air pipe 40, which is opened by second land 45.Thus, the hammer 3 starts to return. In this way, the hammer 3 is movedback in the cylinder 1 and passes by the air inlet 47 again. At thistime, the air pressure at the air inlet 47 drops and the cushion valve49 tends to return the return valve ll to its initial position. However,the operation is delayed due to the flow-resistance of the throttle 51.Consequently, the position of the return valve is changed when thehammer 3 is in an appropriate position on its way back, thus closing theair pipes 39 and 40. From this time on, the hammer 3 moves back due toits own inertia, while compressing the air remaining in the cylinder 1.This compression of air decelerates the hammer 3 to provide cushioningaction to the hammer 3 in the last stage of the hammer return stroke.

The overall operation of the impact hydraulic forming device of theabove-described construction will be described hereinbelow. Now, thehammer 3 has completed its cycle and remains stopped in the positionwhere impacting is completed. First, the operating valve 20 and themotion stop valve 46 are opened. When compressed air is fed into thereturning air ports 18 by the manual change-over of the return valve 41,the hammer 3 is returned to the reciprocating motion starting point. Atthis time, trigger rod 27 of the auxiliary feed valve 26 is pushed tothe right to open the main feed valve 25. Then, compressed air is fedinto the cylinder 1. During the early part of advancing motion, thehammer 3 is advanced by the pressure of this compressed air. In thelatter stage, after the hammer 3 has passed by the cut-off air port 36,the advancing motion of the hammer 3 is accomplished by the expansion ofthe compressed air. During this advancing motion of the hammer 3, thewater supplied from the water source into the plunger hole 8 is sealedtherein by the water flow injected from the water outlet 14 into thewater membrane chamber 6 at a high speed. The plunger 2 is directlythrust to produce the impact hydraulic pressure, by means of which aforming operation is accomplished. At this time, the position of thereturn valve 41 is changed by means of the cushion valve 49. The hammer3 is returned by the dynamic pressure of the air injected from thereturning air ports 18. While the hammer 3 is returning, the returnvalve All makes a return motion. Thus, the hammer 3 completes the returnstroke, while being cushioned, and then the advancing stroke is startedagain. In this way, the hammer 3 repeats the reciprocating motionscontinuously and various kinds of working are continuously performed bymeans of the impact force. The cycle of the hammer is completed when themotion stop valve 46 is closed. The hammer 3 is not returned but stopsits motion at the position where the impacting completed. The operatingvalve is closed. Thus, the operation is completed.

As described above, according to this invention, the direct thrust ofthe plunger 2, in the case where the device is installed horizontally,becomes possible by sealing the water filled in the then horizontalplunger bore 8 so as not to allow it to flow out. In the vertical typedevice, wherein the plunger is adapted to move upward from the bottom,the plunger bore opens downwardly. In this case, the dropping of watercan be prevented by forming a water membrane in the same manner asdescribed hereinbefore. In this construction, it is preferable toprovide a means for blowing air upward from a point near the hydraulicpressure chamber in order to prevent the interior of the cylinder fromrusting due to water splashed from the plunger bore disposed above intothe cylinder disposed below.

Furthermore, in accordance with this invention, the plunger 2 and thehammer 3 are specifically constructed so that the jet effect can beutilized, that the air to be used can be small in amount and low inpressure and that the fatigue strength of the hammer is not decreased byreason of this construction.

Moreover, in accordance with this invention, compressed air is expandedup to a certain predetermined expansion coefficient, and therefore theenergy possessed by compressed air can be effectively and economicallyutilized.

Additionally, in accordance with this invention, the mechanism forreciprocating the hammer comprises the main feed valve 25 for feeding orshutting off the working compressed air, the auxiliary feed valve 26 forcontrolling the main feed valve 25 in conformity with the position ofthe hammer during its advancing motion, the return valve 41 foraccomplishing the reciprocating motion of the hammer, and the cushionvalve 49 for controlling the operation of the return valve 41. Thus, thecontinuous reciprocating motion of the hammer can be repeated smoothlyand successive blows can be effected continuously many times, andconsequently a great deal of work can be done in a short period of time.

In another embodiment illustrated in FIG. 3, an air port 54 is providedinstead of the opening 4 at the front end of the cylinder 1. A valve 57,comprising a valve body 56 biased by a spring 55, is provided at airport 54. An air pipe 58 branched from the air pipe 40 is connected tothe operating side of the valve body 56. Other component parts areconstructed in the same manner as the embodiment described hereinbefore.Thus, when the hammer 3 is advancing, the valve body 56 is pushed by thespring 55 to open the air port 54, thus bringing the cylinder 1 intocommunication with atmosphere. When the hammer 3 starts to return afterthe completion of the advancing motion, compressed air is fed into thereturning air ports 18 and is also applied through the air pipe 58 ontothe valve body 56 of the valve 57 to close the air port 54.Consequently, in comparison with the first embodiment, in which thefront end of the cylinder 1 is always held open, wasteful leakage ofpart of the air injected from the returning air ports 18 at the time ofthe return motion of the hammer 3 is prevented, thus accomplishing thereturn of the hammer 3 effectively.

In still another embodiment illustrated in FIG. 4, a solenoid valve isused as the valve 59' of the water inlet M. The feed valve 9' for theplunger bore 8 also is a solenoid valve. Furthermore, the return valve41', for

the returning air ports 18, and the feed valve 25', for the feed port 19also are solenoid valves. An exhaust valve 61, in the form ofa solenoidvalve, is provided on an air pipe 60 which is branched from the air pipe22 for the feed port 19. An elastic seat 62 is installed at the rear endof the cylinder 1 to provide a cushioning effect for the return of thehammer 3. Provided at the seat 62 are a return detecting rod 64 biasedoutwardly by a spring 63 and protruding into the cylinder 1 and a returnconfirming switch 66 comprising a switch operator 65 operable inconformity with the displacement of the detecting rod 64. Theabove-described valves are all electrically connected by way of acontroller 67 comprising switch 66 and a self-maintaining or holdingcircuit. The advancing motion of the hammer 3 is started by operatingswitch 66. From that time on, the advancing motion is accomplished afterthe feed valve 25' is opened and the return valve 41' and the exhaustvalve 61 are closed by the self-maintaining action of the controller 67.At this time, in the hydraulic pressure chamber 7, the feed valve 9' isclosed and the valve 59' is opened, and therefore the water is filled inthe plunger bore 8 without flowing out. When the advancing motion of thehammer 3 is completed and the return motion is to be started, the feedvalve 25' is closed and the return valve 41' and the exhaust valve 61are opened by means of a timer or the like of the controller 67. Thus,the hammer 3 is returned. When the switch 66 is operated again by thehammer 3, the return motion is completed and the next advancing motionis started. In this way, the reciprocating motion of the hammer 3 iscontinuously accomplished and the same effect as that obtained in thefirst embodiment can be achieved. However, the operation is accomplishedelectrically in the above-described embodiment, the construction can begreatly simplified and the reliability of operation can be improved.

What is claimed is:

1. An impact hydraulic forming device comprising, in combination, ahydraulic pressure chamber having a bore filled with impact hydraulicpressure producing water; a plunger arranged to be thrust into saidbore; a hammer operable to thrust said plunger into said bore and toretract said plunger completely out of said bore; means operable to sealthe water in said bore against discharge therefrom when said plunger isretracted completely out of said bore; means operable to retract saidhammer after thrusting said plunger into said bore, to retract saidplunger; and means operable to reciprocate said hammer cyclically tothrust said plunger into said bore cyclically to produce impacthydraulic pressure repetitively and cyclically.

2. An impact hydraulic forming device, as claimed in claim 1, includinga cylinder in which said hammer is reciprocated; said hammer having adiameter substantially greater than the diameter of said plunger andbeing integral with said plunger; the surface of said hammer facing saidbore and integral with said plunger being formed with an annularcurvilinear cross-section recess merging smoothly with the periphery ofsaid plunger; said cylinder having a wall at its end adjacent said boreand formed with an enlarged aperture through which said plunger extendswith clearance; said wall being formed with a series ofcylinder-returning air ports connected to a source of air under pressureand arranged to direct air supplied thereto as jets directed againstsaid recess substantially parallel to the axis of said plunger and saidhammer; whereby said hammer may be rapidly returned to the retractedposition, upon supply of air under pressure to said ports, by utilizingthe jet effect produced by the air jets striking against said recess.

3. An impact hydraulic forming device, as claimed in claim 2, in whichsaid means operable to reciprocate said hammer cyclically includes afeed port, for air under pressure, in the opposite end of said cylinder;a main feed valve connected between said feed port and a source of airunder pressure to control supply of compressed air to said cylinder toadvance said hammer and plunger; said main feed valve including a springbiased valve body normally closing said feed port and having one endsubjected to the pressure of said source of air under pressure; anauxiliary feed valve controlling connection to atmosphere of theopposite end of said valve body; said auxiliary feed valve beingarranged to connect said opposite end to atmosphere, to provide foropening of said main feed valve by pressure air from said source, duringthe initial stage of the advancing stroke of said hammer, and to supplypressure air to said opposite end to close said main feed valve when apreselected range of the air expansion coefficient has been attainedduring the later part of the advancing stroke of said hammer and duringthe return stroke of said hammer; a return valve connected between saidsource of air under pressure, said cylinder-returning air ports of saidhammer returning means and a port for discharging compressed air duringthe return stroke of said hammer; said return valve being operableselectively to open or to close both said returning air ports and saiddischarge port simultaneously; and a cushion valve connected to saidreturn valve and operable to apply the compressed air in the cylinder,upon completion of the advancing stroke of said hammer, to said returnvalve to open the latter, and to close said return valve beforecompletion of the return stroke of said hammer to trap the remaining airin said cylinder to provide a cushioning effect for the return stroke ofsaid hammer.

4. An impact hydraulic forming device, as claimed in claim 3, whereinall of said valves are operated by working compressed air.

5. An impact hydraulic forming device, as claimed in claim 3, whereinall of said valves are operated by the air pressure in said cylinder.

6. An impact hydraulic forming device, as claimed in claim 3, in whichsaid feed valve is a solenoid valve; an exhaust solenoid valvecontrolling discharge of air from said cylinder; said return valvecomprising a solenoid valve; a hammer-return confirming electric switchoperable by said hammer to confirm the return stroke of said hammer; anda controller connecting said switch and said valves through a holdingcircuit controlled by said switch, in association with timers; all ofsaid valves being selectively opened and closed by electric signalsprovided thereto by said controller, to effect reciprocation of saidhammer in said cylinder.

7. An impact hydraulic forming device comprising, in combination, ahydraulic pressure chamber having a bore filled with impact hydraulicpressure producing water; a plunger arranged to be thrust into saidbore; a

hammer operable to thrust said plunger into said bore; means operable toseal the water in said bore against discharge therefrom when saidplunger is retracted out of said bore; means operable to retract saidhammer after thrusting said plunger into said bore, to retract saidplunger; means operable to reciprocate said hammer cyclically to thrustsaid plunger into said bore cyclically to produce impact hydraulicpressure repetitively and cyclically; feed valve means connected betweensaid bore and a source of water to supply water to said bore; and acylinder in which said hammer is reciprocated; said means operable toseal the water in said bore comprising a water membrane chamberinterposed between the adjacent ends of said bore and said cylinder, awater inlet port in said chamber connected to a source of water underpressure and operable to direct a water jet against the opening of saidbore perpendicular to the axis of said bore and inclined at a smallangle to a diametric plane of said bore to form a water membrane, and anoutlet opposite said water inlet to discharge the water jetted into saidwater membrane chamber after formation of the water membrance; saidwater membrane chamber being formed with an aperture communicating withatmosphere.

1. An impact hydraulic forming device comprising, in combination, ahydraulic pressure chamber having a bore filled with impact hydraulicpressure producing water; a plunger arranged to be thrust into saidbore; a hammer operable to thrust said plunger into said bore and toretract said plunger completely out of said bore; means operable to sealthe water in said bore against discharge therefrom when said plunger isretracted completely out of said bore; means operable to retract saidhammer after thrusting said plunger into said bore, to retract saidplunger; and means operable to reciprocate said hammer cyclically tothrust said plunger into said bore cyclically to produce impacthydraulic pressure repetitively and cyclically.
 2. An impact hydraulicforming device, as claimed in claim 1, including a cylinder in whichsaid hammer is reciprocated; said hammer having a diameter substantiallygreater than the diameter of said plunger and being integral with saidplunger; the surface of said hammer facing said bore and integral withsaid plunger being formed with an annular curvilinear cross-sectionrecess merging smoothly with the periphery of said plunger; saidcylinder having a wall at its end adjacent said bore and formed with anenlarged aperture through which said plunger extends with clearance;said wall being formed with a series of cylinder-returning air portsconnected to a source of air under pressure and arranged to direct airsupplied thereto as jets directed against said recess substantiallyparallel to the axis of said plunger and said hammer; whereby saidhammer may be rapidly returned to the retracted position, upon supply ofair under pressure to said ports, by utilizing the jet effect producedby the air jets striking against said recess.
 3. An impact hydraulicforming device, as claimed in claim 2, in which said means operable toreciprocate said hammer cyclically includes a feed port, for air underpressure, in the opposite end of said cylinder; a main feed valveconnected between said feed port and a source of air under pressure tocontrol supply of compressed air to said cylinder to advance said hammerand plunger; said main feed valve including a spring biased valve bodynormally closing said feed port and having one end subjected to thepressure of said source of air under pressure; an auxiliary feed valvecontrolling connection to atmosphere of the opposite end of said valvebody; said auxiliary feed valve being arranged to connect said oppositeend to atmosphere, to provide for opening of said main feed valve bypressure air from said source, during the initial stage of the advancingstroke of said hammer, and to supply pressure air to said opposite endto close said main feed valve when a preselected range of the airexpansion coefficient has been attained during the later part of theadvancing stroke of said hammer and during the return stroke of saidhammer; a return valve connected between said source of air underpressure, said cylinder-returning air ports of said hammer returningmeans and a port for discharging compressed air during the return strokeof said hammer; said return valve being operable selectively tO open orto close both said returning air ports and said discharge portsimultaneously; and a cushion valve connected to said return valve andoperable to apply the compressed air in the cylinder, upon completion ofthe advancing stroke of said hammer, to said return valve to open thelatter, and to close said return valve before completion of the returnstroke of said hammer to trap the remaining air in said cylinder toprovide a cushioning effect for the return stroke of said hammer.
 4. Animpact hydraulic forming device, as claimed in claim 3, wherein all ofsaid valves are operated by working compressed air.
 5. An impacthydraulic forming device, as claimed in claim 3, wherein all of saidvalves are operated by the air pressure in said cylinder.
 6. An impacthydraulic forming device, as claimed in claim 3, in which said feedvalve is a solenoid valve; an exhaust solenoid valve controllingdischarge of air from said cylinder; said return valve comprising asolenoid valve; a hammer-return confirming electric switch operable bysaid hammer to confirm the return stroke of said hammer; and acontroller connecting said switch and said valves through a holdingcircuit controlled by said switch, in association with timers; all ofsaid valves being selectively opened and closed by electric signalsprovided thereto by said controller, to effect reciprocation of saidhammer in said cylinder.
 7. An impact hydraulic forming devicecomprising, in combination, a hydraulic pressure chamber having a borefilled with impact hydraulic pressure producing water; a plungerarranged to be thrust into said bore; a hammer operable to thrust saidplunger into said bore; means operable to seal the water in said boreagainst discharge therefrom when said plunger is retracted out of saidbore; means operable to retract said hammer after thrusting said plungerinto said bore, to retract said plunger; means operable to reciprocatesaid hammer cyclically to thrust said plunger into said bore cyclicallyto produce impact hydraulic pressure repetitively and cyclically; feedvalve means connected between said bore and a source of water to supplywater to said bore; and a cylinder in which said hammer is reciprocated;said means operable to seal the water in said bore comprising a watermembrane chamber interposed between the adjacent ends of said bore andsaid cylinder, a water inlet port in said chamber connected to a sourceof water under pressure and operable to direct a water jet against theopening of said bore perpendicular to the axis of said bore and inclinedat a small angle to a diametric plane of said bore to form a watermembrane, and an outlet opposite said water inlet to discharge the waterjetted into said water membrane chamber after formation of the watermembrance; said water membrane chamber being formed with an aperturecommunicating with atmosphere.